Removing vitreous lubricant from metal



United States Patent REMOVING VITREOUS LUBRICANT FROM METAL Emerson N. Ludington, West Haven, Conn., assignor to Bridgeport Brass Company, Bridgeport, Conn., a corporation of Connecticut No Drawing. Application March 23, 1953, Serial No. 344,183

6 Claims. (Cl. 1343) This invention relates to the removal of vitreous lubricant from metal which has been hot-worked under pressure against the lubricant. Such a vitreous lubricant is used between a die surface and the metal being worked when high working temperatures and pressures are involved. The vitreous lubricant under the heat and pressure becomes fiuid and provides a lubricating film reducing the working pressures otherwise required and protecting the die against the heat of the metal.

The metal product resulting from the above retains some of the vitreous lubricant on its surface. This may be in the form of a scale-like or spotty layer and obviously requires removal before the metal can be worked further by other tools.

Such a vitreous lubricant ordinarily comprises a glass of special composition fitting it for this specialized kind of use but still retaining many of the characteristics of ordinary glass. Conventional mill pickling liquors or solutions, of course, do not normally attack glass. Hydrofiuoric acid dissolves'glass but is a dangerous material to store and use.

One of the objects of the present invention is to provide a safe and practical process for removing the vitreous or glass-like lubricant from the metal which has been hot-Worked under pressure against the lubricant. The use of a vitreous lubricant in a cuprous metal extrusion press presents the described problem with particular severity, it being necessary to further work both the extruded rod and tube, frequently by drawing the product through a die which would be rapidly destroyed by the vitreous lubricant. Another object of the invention is to provide the described kind of process in a form which is particularly effective in removing the vitreous lubricant from extruded cuprous rod, tube and other shapes produced by an extrusion press.

Generally speaking, the present invention is based on the discovery that if the metal carrying the vitreous lubricant is quenched from an elevated temperature rapidly to room temperature it becomes possible to remove the lubricant by pickling the metal in a pickling solution in which the lubricant is substantially insoluble prior to B being used as a lubricant during the hot-working of the "metal.

It is to be understood that glass in general academically speaking is soluble in many liquids, even including water, but this degree of solubility is so slight or slow that it is reasonable to say that the glass is insoluble.

The ordinary pickling liquors or solutions used in a mill specializing in cuprous metal, consists of from 3% to 15% sulphuric acid water solution, used hot or cold, or a Water solution of from 2% to 12% of both sodium dichromate and sulphuric acid, normally used cold, and sometimes other solutions, in all of which glass is for practical purposes insoluble. .Therefore, these materials have been considered unsuitable for use in connection with removing the vitreous lubricant. However, by

rapidly quenching the cuprous metal from temperatures ranging from 750 C. to 1000 C., the vitreous lubricant is conditioned so that it may be removed in a' practical manner by pickling the metal in the pickling liquors or solutions mentioned above.

As a specific example of the process of the present invention, cuprous metal has been extruded from an appropriate extrusion press using the glass lubricant between the working face of the die and the billet. The extruded product had a temperature of between 750 C. to 1000 C. As soon as possible after the extrusion the metal was quenched to room temperature at a relatively rapid but practical quenching rate. Thereafter pickling in either the sulphuric acid solution or the sodium dichromate and sulphuric acid solution, previously described, and using only usual mill pickling practices, serves to remove the vitreous lubricant. Thereafter the extruded product may be drawn through a die or otherwise worked as desired.

in the above the vitreous lubricant used may be various combinations of oxides of the general character usually found in glasses. Such oxides as SiOz, B203, Na2O are known to be present in these glasses although the exact composition is unknown. Other glasses containing these or other oxides in diflferent proportions which have been used as a lubricant, have also been removed successfully by the above procedure.

It is believed that the action of the pickle after the quench is first to dissolve some of the metal and its oxides to loosen some of the glass, and secondly a chemical attack on the glass itself which has presumably been modified in some fashion during the extrusion. This explanation is based on theory only.

It is also believed that the quenching action fragmentates the glass layer or pieces on the extruded metal, which accelerates the above first described action. In addition, however, the glass appears to be changed chemically so that while initially substantially insoluble in the ordinary pickling liquors described, it becomes soluble to a substantial degree as the result of the effects of the extrusion action.

It can be seen from the foregoing that the present invention provides a very practical process, involving no steps unusual to mill operators, for easily and rapidly removing the vitreous lubricant from metal which has been hot-worked under pressure against the lubricant.

I claim:

1. A process for removing vitreous lubricant from metal which has been hot-worked under pressure against the lubricant, the process including quenching the metal from an elevated temperature and thereafter pickling the metal in a pickling solution in which the lubricant is substantially insoluble prior to the hot-working, said metal being cuprous and said solution being of the class consisting of water solutions of sulphuric acid, and of sulphuric acid and sodium dichromate.

2. A process for removing vitreous lubricant from metal extruded hot from a metal extrusion press using the lubricant, the process including quenching the hot extruded metal and thereafter pickling the metal in pickling liquor in which the lubricant is substantially insoluble prior to its use in the press, the metal being cuprous and the liquor being of the class consisting of water solutions of sulphuric acid and of sulphuric acid and sodium dichromate.

3. A process for removing vitreous lubricant from metal extruded hot from a metal extrusion press using the lubricant, the process including quenching the hot extruded metal and thereafter pickling the metal in pickling liquor in which the lubricant is substantially insoluble prior to its use in the press, the metal being cuprous and the liquor being of the class consisting of water solutions of sulphuric acid and of sulphuric acid and sodium dich'romate; the metal being at a temperatureof 750 C. to 1000 C. when quenched.

4. A process for removing vitreous lubricant from metal which has been hot-worked under pressure against the lubricant, the process including pickling the metal in a pickiing liquor in which the lubricant is substantially insoluble prior to the said'hotworking the metal being cuprous and the liquor being of the class consisting of water solutions of sulphuric acid and of sulphuric acid and sodium dichromate.

5. A process for removing vitreous Lubricant from cuprous metal extruded hot from a metal extrusion press using the lubricant, the process including pickling the extruded cuprous metal in a pickling liquor in which the lubricant-is substantially insoluble prior to its use in the press, the liquor being of the class consisting of water solutions of sulphuric acid and of sulphuric acid and sodium dichrornate.

6. A process for removing vitreous lubricant from cuprous metal extruded hot from a metal extrusion press using the lubricant, the process including pickling the extruded cuprous metal in a pickling liquor in which the lubricant is substantially insoluble prior to its use in the press, the liquor being of the class consisting of from 3% to 15% sulphuric acid water solution and a water solution of from 2% to 12% of both sodium dichromate and sulphuric acid.

Bassett July 28, 1942 Caugherty Ian. 4, 1944 

1. A P ROCESS FOR REMOVING VITREOUS LUBRICANT FROM METAL WHICH HAS BEEN HOT-WORKED UNDER PRESSURE AGAINST THE LUBRICANT, THE PROCESS INCLUDING QUENCHING THE METAL FROM AN ELEVATED TEMPERATURE AND THEREAFTER PICKLING THE METAL IN A PICKLING SOLUTION IN WHICH THE LUBRICANT IS SUBSTANTIALLY INSOLUBLE PRIOR TO THE HOT-WORKING, SAID METAL BEING CUPROUS AND SAID SOLUTION BEING OF THE CLASS CONSISTING OF WATER SOLUTIONS OF SULPHURIC ACID, AND OF SULPHURIC ACID AND SODIUM DICHROMATE. 